DEA-C01 Data Operations and Support Practice Question
A company uses Amazon Redshift for data warehousing. They notice that query performance has degraded over time. Which maintenance operation should be performed to improve performance?
⚠ Common exam trap
DEA-C01 often tests the distinction between VACUUM (space reclamation and sort) and ANALYZE (statistics update), causing candidates to choose ANALYZE when the issue is performance degradation due to fragmentation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run the VACUUM command
The VACUUM command in Amazon Redshift reclaims space from deleted rows and re-sorts rows to restore the sort order, which improves query performance by reducing I/O and enabling more efficient scans. Over time, as data is updated or deleted, the physical storage becomes fragmented and sort order degrades, leading to slower queries. Running VACUUM (or VACUUM SORT ONLY, VACUUM DELETE ONLY, etc.) is the recommended maintenance operation to address this degradation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Run the VACUUM command
Why this is correct
VACUUM reclaims space from deleted rows and re-sorts unsorted data, restoring the physical ordering that Redshift's zone maps rely on for block skipping. Degraded performance from accumulated deletes and unsorted loads is exactly the maintenance gap it addresses, so it satisfies the stem's requirement directly.
- ✗
Drop and recreate the table
Why it's wrong here
Dropping and recreating the table discards all data and statistics, so it cannot restore query performance without a full reload. It is tempting when a table is corrupt or its distribution style is fundamentally wrong, where a CTAS rebuild genuinely is the correct remedy.
- ✗
Run the REINDEX command
Why it's wrong here
REINDEX rebuilds indexes to repair corruption or bloat, but it does not restore the sort order of table rows, which is what degrades zone-map effectiveness after loads. VACUUM SORT is the operation that re-sorts unsorted rows and would be correct after heavy ingestion.
- ✗
Run the ANALYZE command
Why it's wrong here
ANALYZE refreshes table statistics so the query planner can choose optimal plans, which is the standard remedy for gradual performance degradation. It is tempting because it addresses stale statistics, but it does not reclaim space from deleted rows or fix unsorted data, which VACUUM handles.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.